This invention relates in general to jacket seals, and in particularly to seals (gaskets) suitably used with pipes or containers which are internally evacuated of air.
In the field of semiconductor, it is desired to completely eliminate any foreign materials present in a product, to enhance vacuum and to make the inside of pipes for vacuum drawing to be cleaner in order to manufacture high-performance products capable of performing advanced technology functions. Accordingly, even in the case of seals for use in joints of pipes or the like for vacuum drawing, such a seal is required not to give off, from itself, gas or particles into the pipe.
In the case of using an O ring of rubber as a seal, the components of the rubber ring are emitted, by vacuum drawing, into a pipe in a gaseous form or in a particle form. Also, a gas outside the pipe permeates through the rubber and enters into the pipe. Accordingly, rubber O rings are unfit for vacuum seals. The rubber O ring is not suitably used where a fluid, which attacks rubber, flows through the pipe, either. On the other hand, an O ring of metal emits no foreign materials of the type described above. The metal O rings however, requires heavier clamping pressure to perform an effective seal function. It is therefore essential to provide a mechanism capable of achieving a heavy clamping pressure at joint portions of a vacuum apparatus. This, however, produces the problem that the apparatus itself increases in size. In order to enhance the clamping pressure, for example, the number of clamping bolts must be increased, which may cause some problems in construction that layout space for bolts cannot be reserved and that members being sealed hardly sustains the clamping pressure. Thus, the apparatus increases in size.
To cope with such a problem, as shown in FIGS. 13 and 14, a jacket seal, which emits no foreign material into a space 30 being sealed, which involves no gas permeation and which requires no heavy seal clamping pressure, is employed. In the jacket seal, an elastic member 1 having a cross section of circular shape is accommodated in a metal jacket 2 which has, at its outer peripheral surface, an opening portion 23, and projections 25 and 25 having a cross section of triangular shape are annularly formed on surfaces 21 and 21 being squeezingly compressed (exterior surfaces of flange portions) of the metal jacket 2, these surfaces 21 and 21 being in opposite relationship with seal surfaces of members being. sealed.
In such a jacket seal, an inner peripheral surface 24 and the being-compressed surfaces 21 and 21 are all formed of metal, so that inclusion of foreign materials into the being-sealed space 30 is unlikely to occur. Furthermore, the projection 25 of the being-compressed surface 21 has a vertex point which abuts against the seal surface of the being-sealed member and which is then crushed by seal clamping pressure to come into close contact with the seal surface of the being-sealed member. Meanwhile, the metal jacket 2 is deflected by seal clamping pressure such that the opening portion 23 is made narrower. At the same time, the elastic member 1 held in the metal jacket 2 also undergoes compressive deformation, as a result of which reaction force against the seal clamping pressure can be obtained from the metal jacket 2 and from the elastic member 1. Accordingly, such a jacket seal makes it possible to obtain sufficient seal effects without the necessity of achieving a heavy clamping pressure.
In a conventional jacket seal, in order to obtain high seal performance with small clamping pressure, it is arranged such that the projection 25 having a cross section of triangular shape has a vertex point which is finished relatively sharp so that the projection 25 is easily crushed and small clamping pressure is concentrated on the vertex point to improve sealability. In addition, in order to hold down costs, an O ring of rubber superior in versatility is also used as the elastic member 1 that is accommodated in the metal jacket.
However, the performance of jacket seals may vary depending on the machining accuracy of the metal jacket 2. For example, as shown in FIG. 16(a), if the position of a vertex point T of the projection 25 formed on the being-compressed surface 21 of the metal jacket 2 in opposing relationship with the seal surface 32 of the being-sealed member, deviates from a centerline m in a cross section of the elastic member 1 accommodated in the metal jacket 2, then proper reaction force will not be obtained from the elastic member 1 upon application of clamping pressure, so that a flange portion of the metal jacket 2 itself may distort to undergo plastic deformation, as shown in FIG. 16(b). Accordingly, in some cases, a desired seal performance is not obtained. Moreover, once a jacket seal has undergone plastic deformation, it is impossible to reuse such a plastically-deformed seal, which means that when disassembling a pipe joint for the purpose of maintenance/inspection or the like, there is produced the problem that a new jacket seal must be prepared, which is uneconomical.
Moreover, the projection 25, formed on the being-compressed surface 21 of the metal jacket 2, is finished sharp pointed for the purpose of improving sealability. However, when the projection 25 is finished sharp pointed, a burr or a flash is created at an endmost portion of the projection 25, which results in poor machining accuracy. Accordingly, when clamped, the projection 25 will not be crushed uniformly over its full length, and, as shown in FIG. 15, in the projection thus crushed, two sections are mixedly present. More specifically, one of the sections (indicated by solid line) results from the collapse of the end T of the projection 25 from its original position Txe2x80x2 prior to the crush toward P (the inside (central side) of the seal), while the other of the sections (indicated by broken line) results from the collapse of T from Txe2x80x2 toward R (the outside of the seal). Therefore a target seal performance cannot be achieved at a point of inflection where the direction, in which the projection 25 collapses, changes from the side P to the side R, and a phenomenon, in which there occurred a drop in the seal performance, was observed.
Accordingly, an object of the present invention is to provide solutions to these problems.
Moreover, another object of the present invention is to constantly achieve high seal performance without requiring high machining accuracy.
Furthermore, still another object of the present invention is to provide a jacket seal which is stable in quality and which can be reused.
In order to solve the above-described problem, the present invention discloses a jacket seal comprising (a) a metal jacket having an annular web portion and a pair of flange portions projecting outward from sides of the web portion, respectively, and (b) an elastic member accommodated in the metal jacket,
wherein the metal jacket includes a projection which is annularly formed at an exterior surface of each of the flange portions and which abuts against a seal surface of a member being sealed (i.e., a pipe or a container to be sealed), and
the elastic member includes a flat portion which abuts against an interior surface of each of the flange portions of the metal jacket.
In the jacket seal of the present invention, the flat portion is in surface-to-surface contact with a position of the interior surface of each of the flange portions of the metal jacket corresponding to the projection.
In the jacket seal of the present invention, the projection has a cross section of approximately triangular shape whose vertex angle is 50 degrees or more.
The present invention discloses a jacket seal comprising (a) a metal jacket having an annular web portion and a pair of flange portions projecting outward from sides of the web portion, respectively, and (b) an elastic member accommodated in the metal jacket,
wherein the metal jacket includes a projection which is annularly formed at an exterior surface of each of the flange portions and the projection has a vertex portion which is formed flat over the full circumferential length so as to abut against a seal surface of a member being sealed.
In the jacket seal of the present invention in which the projection vertex portion is formed flat, the elastic member includes a flat portion which abuts against a position of an interior surface of each of the flange portions of the metal jacket corresponding to the projection.
In the jacket seals of the present invention, the elastic member has a cross section of approximately D-letter shape.
The present invention discloses a jacket seal comprising (a) a metal jacket having an annular web portion and a pair of flange portions projecting outward from sides of the web portion, respectively, and (b) an annular elastic member accommodated in the metal jacket,
wherein the metal jacket includes a projection which is annularly formed at an exterior surface of each of the flange portions and which abuts against a seal surface of a member being sealed, and
the elastic member includes a contact portion which establishes contact with a position of an interior surface of each of the flange portions of the metal jacket corresponding to the projection at a width greater than the width of the projection and at an approximately uniform pressure, in a relaxed state in which no clamping pressure is acting on the metal jacket.
The present invention discloses a jacket seal comprising (a) a metal jacket having an annular web portion and a pair of flange portions projecting inward or outward from sides of the web portion, respectively, and (b) an annular elastic member accommodated in the metal jacket, the jacket seal being clamped between seal surfaces of members being sealed and, in order to prevent components of the elastic member from being emitted into either one of an inner space and an outer space, the web portion is directed toward one of the spaces and the flange portions at both sides thereof are formed so as to project toward the other of the spaces, thereby to prevent a fluid from communicating between the inner space and the outer space,
wherein the metal jacket includes a projection which is annularly formed at an exterior surface of each of the flange portions and which abuts against the seal surface, and
the elastic member establishes surface-to-surface contact with a position of an interior surface of each of the flange portions of the metal jacket corresponding to the projection at a width greater than the width of the projection, in a relaxed state in which no clamping pressure is acting on the metal jacket.
The present invention discloses a jacket seal comprising (a) a metal jacket having an annular web portion and a pair of flange portions projecting outward from sides of the web portion, respectively, and (b) an annular elastic member accommodated in the metal jacket,
wherein the metal jacket includes a projection which is annularly formed at an exterior surface of each of the flange portions and which abuts against a seal surface of a member being sealed,
the elastic member includes a contact portion which establishes contact the a position of an interior surface of each of the flange portions of the metal jacket corresponding to the projection at an approximately uniform pressure, in a relaxed state in which no clamping pressure is acting on the metal jacket, and
an endmost portion of the projection is positioned within a region corresponding to the width of the contact portion.
The present invention discloses a jacket seal comprising (a) a metal jacket having an annular web portion and a pair of flange portions projecting inward or outward from sides of the web portion, respectively, and (b) an annular elastic member accommodated in the metal jacket, the jacket seal being clamped between seal surfaces of members being sealed and, in order to prevent components of the elastic member from being emitted into either one of an inner space and an outer space, the web portion is directed toward one of the spaces and the flange portions at both the sides thereof are formed so as to project toward the other of the spaces, thereby to prevent a fluid from communicating between the inner space and the outer space,
wherein the metal jacket includes a projection which is annularly formed at an exterior surface of each of the flange portions and which abuts against the seal surface,
the elastic member establishes surface-to-surface contact with a position of an interior surface of each of the flange portions of the metal jacket corresponding to the projection, in a relaxed state in which no clamping pressure is acting on the metal jacket, and
an endmost portion of the projection is positioned within a region corresponding to the width of the surface-to-surface contact.
The present invention discloses a jacket seal comprising a metal jacket having an annular web portion and a pair of flange portions projecting inward or outward from sides of the web portion, respectively, and
an elastic member formed by filling unvulcanized rubber into the metal jacket over the full circumferential length thereof and subjecting the filled unvulcanized rubber to vulcanization so as to be adhered to interior surfaces of the web portion and the flange portions at both the sides of the web portion.
In the jacket seal of the present invention making utilization of the foregoing unvulcanized rubber, the metal jacket includes a projection which is annularly formed at an exterior surface of each of the flange portions and which abuts against a seal surface of a member being sealed.
In the jacket seal in accordance with the present invention, it is arranged such that the elastic member includes a flat portion which abuts against an interior surface of each of the flange portions of the metal jacket, which results in that the contact area of the elastic member with respect to each of the flange portions of the metal jacket increases and the contact surface comes to have a certain width. Therefore, reaction force against clamping pressure can stably be obtained without having to achieve a close correspondence between the vertex point of a projection of one of the flange portions and the vertex point of a projection of the other of the flange portions in a direction in which clamping pressure is applied. Moreover, with the flat portion which abuts against the interior surface of each of the flange portions, it is no longer necessary to specifically arrange the vertex point of the projection on a cross-sectional centerline of the elastic member and no high machining accuracy is required at a position where the projection is formed, even when employing, as an elastic member, a rubber O ring having a cross section of approximately circular shape. Moreover, the flange portions of the metal jacket are held in plane by the elastic member, which therefore prevents the flange portions from being plastically deformed.
Particularly, if the foregoing flat portions are formed in such a way as to come to abut against a position of the interior surface of each of the flange portions of the metal jacket corresponding to the projection, this provides the advantage of stably achieving reaction force against clamping pressure, and it is sufficient that the vertex point of the projection is provided within the surface-to-surface contact width in point. Moreover, it is preferable to form the flat portion over the full circumferential length of the elastic member in order to stably obtain clamping reaction force.
Additionally, also in the case of forming a contact portion in the elastic member which establishes contact with a position of the interior surface of each of the flange portions of the metal jacket corresponding to the projection at a width greater than the width of the projection and at an approximately uniform pressure in a relaxed state in which no clamping pressure is acting on the metal jacket, the same operation effects as in the case in which the foregoing flat portion is formed can be obtained. Also in this case, it is preferable to form the contact portion over the full circumferential length of the elastic member in order to stably obtain clamping reaction force.
In addition, even with the contact portion having a narrower width than that of the projection, the similar effects in case with the flat portion can be attained if the endmost portion of the projection is positioned within the region corresponding to the width of the contact portion.
Further, also when the foregoing elastic member is brought into surface-to-surface contact with a position of the interior surface of each of the flange portions of the metal jacket corresponding to the projection at a width greater than the width of the projection in a relaxed state in which no clamping pressure is being applied to the metal jacket, the same operation effects as in the case in which the foregoing flat portion is formed can be obtained. It is preferable for the elastic member to be brought into surface-to-surface contact with an inner peripheral surface of each of the flange portions, over the full circumferential length.
In addition, even with the surface-to-surface contact having a narrower width than that of the projection, the similar effects in case with the flat portion can be attained if the endmost portion of the projection is positioned within the region corresponding to the width of the surface-to-surface contact.
Although the foregoing elastic member is not necessarily brought into contact with an interior surface of the web portion of the metal jacket, such contacting with the interior surface of the web portion, particularly contacting with the entire inner peripheral surfaces of the flange and web portions, will produce the advantage of stably obtaining the foregoing clamping reaction force. When a metal jacket has a cross section of laterally-collapsed U-letter shape defined by the web portion and the pair of flange portions of the metal jacket, in other words, when the metal jacket has a cross section of D-letter shape without a vertical stroke line thereof, if the elastic member is formed to have a cross section of D-letter shape, that is, if a D ring is employed as the elastic member, this makes it possible to bring the elastic member into surface-to-surface contact with substantially the entire inner peripheral surface of the metal jacket.
Moreover, if it is arranged such that the projection has a cross section of approximately triangular shape whose vertex angle is set at 50 degrees or more, this arrangement facilitates forming of a projection end portion to a further extent in comparison with when the vertex angle is set at not more than 50 degrees, and therefore reduces variation in the machining accuracy at the projection end portion without the drop in seal performance.
Additionally, if it is arranged such that the vertex portion of the projection is formed flat over the full circumferential length so as to come to abut against a seal surface of a member being sealed, then the post-clamping direction in which the projection is crushed will be stable without requiring high machining accuracy. In other words, the entire vertex portion of the projection is uniformly crushed by a surface to be compressed squeezingly, thereby eliminating the presence of a mixture of directions in which the projection end collapses as described previously. Accordingly, a desired seal performance can be obtained and variations in the sealability from one product to another is eliminated thereby to improve seal productivity.
Moreover, if it is arranged such that the vertex portion of the projection is formed flat and that the elastic member is provided with a flat portion which abuts against an inner peripheral surface of each of the flange portions of the metal jacket, then the vertex portion of the projection will undergo a stable crush as described above and reaction force against clamping pressure can stably be obtained, whereby a target seal performance can be obtained easily without requiring high machining accuracy for the position and the end shape of the projection. As a result, the variation in jacket seal performance by machining accuracy can be controlled and the problem that the flange portions of the metal jacket undergo plastic deformation can be dispelled.
Further, since it is possible to control the plastic deformation of the flange portions, this makes it possible to reuse a jacket seal depending on its state of use. Accordingly, when disassembling equipment such as a pipe joint to which the present jacket seal has been applied for the purpose of inspection and maintenance, there is no need to prepare a new jacket seal, which is also advantageous in view of the economical aspect.
Moreover, a jacket seal, in which an elastic member having a cross section of D-letter shape is filled into the foregoing metal jacket having a cross section of laterally-collapsed U-letter shape, may be formed as follows. First, unvulcanized rubber is filled into the metal jacket over the full circumferential length of the jacket and the unvulcanized rubber thus filled is subjected to vulcanization so as to be adhered to interior surfaces of the web portion and the flange portions at both sides of the web portion of the metal jacket. Because of such arrangement, there is no need to prepare a metal mold used to manufacture a D ring, which is cost effective.
As a material for the elastic member that is accommodated in the metal jacket, (a) rubber such as natural rubber, ethylene propylene rubber, ethylene propylene diene rubber, acrylonitrile-butadiene rubber, hydrogenated acrylonitrile-butadiene rubber, styrene-butadiene rubber, silicone rubber, chroloprene rubber, chlorosulfonated polyethylene rubber, fluorine rubber, fluoridated silicone rubber, acrylic rubber, and ethylene acrylic rubber or its crosslinked rubber, (b) thermoplastic elastomer such as thermoplastic elastomer of the polystyrene system, thermoplastic elastomer of the polyolefin system, thermoplastic elastomer of the polyvinyl chloride system, and thermoplastic elastomer of the polyester system, and (c) expanded plastic can be used and it is preferable to use materials which exhibit no crystal melting point on the differential calorimetry curve in a differential scanning calorimeter (DSC).
The elastic member can be manufactured by, for example, press- or injection-molding a composition obtained by blending, as necessity requires, conventional amounts of agents normally used in the manufacturing of elastic members, such as antioxidant agents, antiaging agents, reinforcing agents (e.g., carbon black), talc, fillers (e.g., clay), crosslinking agents, crosslinking assist agents, crosslinking accelerators, and processing aids. The elastic member 1 made of a crosslinked rubber is heat crosslinked in a molding step of a press or injection molding process.
As a metal used to form the metal jacket, various metals can be used except for metals which exhibit thermal instability, chemical instability, or mechanical instability in a seal use environment. Especially, hard or soft metals (e.g., metals having relatively good machinability including aluminum, aluminum alloy, copper, copper alloy, and magnesium alloy and metal-ceramic composite) can preferably be used so that an opening portion formed in the metal jacket can be narrowed by relatively small clamping pressure. Additionally, it is preferred that the metal jacket is formed using a material which is softer than a being-sealed member or a material which is plastically deformed easily in order that the projection may be crushed when forced by pressure into contact with a seal surface of the being-sealed member.